Results 1 to 5 of 5

Math Help - determinantQnine

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    19

    determinantQnine

    find the determinant of the matrices below by inspection.give reson in each case.

    B=
    row1 2 7 -3 1
    row2 0 3 7 4
    row3 3 5 -12 1
    row4 4 14 -6 2

    C=
    row1 a b c
    row2 0 e f
    row3 0 0 d


    D=
    row1 3 0 0
    row2 0 -2 0
    row3 0 0 -1


    how to do it by inspection?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Dec 2008
    Posts
    111
    Dear mathseek,

    by B look at the first and the 4th row.

    C = a*e*d
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Banned
    Joined
    Dec 2008
    Posts
    15

    determinantqnine

    plse explain i don't get it !
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Dec 2008
    Posts
    111
    Dear trythis, who are u?

    statement:det(A) is surely 0 if one row is equal an other row multiplying by a number.

    You can check the formula C = a*e*d easily with usage of determinant's definition.

    D applys from C.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by mathseek View Post
    find the determinant of the matrices below by inspection.give reson in each case.

    B=
    row1 2 7 -3 1
    row2 0 3 7 4
    row3 3 5 -12 1
    row4 4 14 -6 2
    row 1 is 2 times row 4, hence matrix is singular do det =???

    C=
    row1 a b c
    row2 0 e f
    row3 0 0 d
    Look at all those zeros, if you expand about the first column rather than the first row there is only one non-zero term.

    D=
    row1 3 0 0
    row2 0 -2 0
    row3 0 0 -1
    same idea as for C

    CB
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum